The emission and dynamics of droplets from human expiratory activities and COVID-19 transmission in public transport system: A review

Qiaoqiao Wang; Jianwei Gu; Taicheng An

doi:10.1016/j.buildenv.2022.109224

The emission and dynamics of droplets from human expiratory activities and COVID-19 transmission in public transport system: A review

Build Environ. 2022 Jul 1:219:109224. doi: 10.1016/j.buildenv.2022.109224. Epub 2022 May 24.

Authors

Qiaoqiao Wang^{1

2}, Jianwei Gu^{3

4}, Taicheng An^{3

4}

Affiliations

¹ Institute for Environmental and Climate Research, Jinan University, 511443, Guangzhou, China.
² Guangdong-Hong Kong-Macau Joint Laboratory of Collaborative Innovation for Environmental Quality, 511443, Guangzhou, China.
³ Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, 510006, Guangzhou, China.
⁴ Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, School of Environmental Science and Engineering, Guangdong University of Technology, 510006, Guangzhou, China.

Abstract

The public transport system, containing a large number of passengers in enclosed and confined spaces, provides suitable conditions for the spread of respiratory diseases. Understanding how diseases are transmitted in public transport environment is of vital importance to public health. However, this is a highly multidisciplinary matter and the related physical processes including the emissions of respiratory droplets, the droplet dynamics and transport pathways, and subsequently, the infection risk in public transport, are poorly understood. To better grasp the complex processes involved, a synthesis of current knowledge is required. Therefore, we conducted a review on the behaviors of respiratory droplets in public transport system, covering a wide scope from the emission profiles of expiratory droplets, the droplet dynamics and transport, to the transmission of COVID-19 in public transport. The literature was searched using related keywords in Web of Science and PubMed and screened for suitability. The droplet size is a key parameter in determining the deposition and evaporation, which together with the exhaled air velocity largely determines the horizontal travel distance. The potential transmission route and transmission rate in public transport as well as the factors influencing the virus-laden droplet behaviors and virus viability (such as ventilation system, wearing personal protective equipment, air temperature and relative humidity) were also discussed. The review also suggests that future studies should address the uncertainties in droplet emission profiles associated with the measurement techniques, and preferably build a database based on a unified testing protocol. Further investigations based on field measurements and modeling studies into the influence of different ventilation systems on the transmission rate in public transport are also needed, which would provide scientific basis for controlling the transmission of diseases.

Keywords: COVID-19; Dynamic; Public transport; Respiratory droplet; SARS-CoV-2; Transmission.

Publication types

Review